1  /* pselect - synchronous I/O multiplexing
       2  
       3     Copyright 2011-2023 Free Software Foundation, Inc.
       4  
       5     This file is part of gnulib.
       6  
       7     This file is free software: you can redistribute it and/or modify
       8     it under the terms of the GNU Lesser General Public License as
       9     published by the Free Software Foundation; either version 2.1 of the
      10     License, or (at your option) any later version.
      11  
      12     This file is distributed in the hope that it will be useful,
      13     but WITHOUT ANY WARRANTY; without even the implied warranty of
      14     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      15     GNU Lesser General Public License for more details.
      16  
      17     You should have received a copy of the GNU Lesser General Public License
      18     along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
      19  
      20  /* written by Paul Eggert */
      21  
      22  #include <config.h>
      23  
      24  #include <sys/select.h>
      25  
      26  #include <errno.h>
      27  #include <signal.h>
      28  
      29  /* Examine the size-NFDS file descriptor sets in RFDS, WFDS, and XFDS
      30     to see whether some of their descriptors are ready for reading,
      31     ready for writing, or have exceptions pending.  Wait for at most
      32     TIMEOUT seconds, and use signal mask SIGMASK while waiting.  A null
      33     pointer parameter stands for no descriptors, an infinite timeout,
      34     or an unaffected signal mask.  */
      35  
      36  #if !HAVE_PSELECT
      37  
      38  int
      39  pselect (int nfds, fd_set *restrict rfds,
      40           fd_set *restrict wfds, fd_set *restrict xfds,
      41           struct timespec const *restrict timeout,
      42           sigset_t const *restrict sigmask)
      43  {
      44    int select_result;
      45    sigset_t origmask;
      46    struct timeval tv, *tvp;
      47  
      48    if (nfds < 0 || nfds > FD_SETSIZE)
      49      {
      50        errno = EINVAL;
      51        return -1;
      52      }
      53  
      54    if (timeout)
      55      {
      56        if (! (0 <= timeout->tv_nsec && timeout->tv_nsec < 1000000000))
      57          {
      58            errno = EINVAL;
      59            return -1;
      60          }
      61  
      62        tv.tv_sec = timeout->tv_sec;
      63        tv.tv_usec = (timeout->tv_nsec + 999) / 1000;
      64        tvp = &tv;
      65      }
      66    else
      67      tvp = NULL;
      68  
      69    /* Signal mask munging should be atomic, but this is the best we can
      70       do in this emulation.  */
      71    if (sigmask)
      72      pthread_sigmask (SIG_SETMASK, sigmask, &origmask);
      73  
      74    select_result = select (nfds, rfds, wfds, xfds, tvp);
      75  
      76    if (sigmask)
      77      {
      78        int select_errno = errno;
      79        pthread_sigmask (SIG_SETMASK, &origmask, NULL);
      80        errno = select_errno;
      81      }
      82  
      83    return select_result;
      84  }
      85  
      86  #else /* HAVE_PSELECT */
      87  # include <unistd.h>
      88  # undef pselect
      89  
      90  int
      91  rpl_pselect (int nfds, fd_set *restrict rfds,
      92               fd_set *restrict wfds, fd_set *restrict xfds,
      93               struct timespec const *restrict timeout,
      94               sigset_t const *restrict sigmask)
      95  {
      96    int i;
      97  
      98    /* FreeBSD 8.2 has a bug: it does not always detect invalid fds.  */
      99    if (nfds < 0 || nfds > FD_SETSIZE)
     100      {
     101        errno = EINVAL;
     102        return -1;
     103      }
     104    for (i = 0; i < nfds; i++)
     105      {
     106        if (((rfds && FD_ISSET (i, rfds))
     107             || (wfds && FD_ISSET (i, wfds))
     108             || (xfds && FD_ISSET (i, xfds)))
     109            && dup2 (i, i) != i)
     110          return -1;
     111      }
     112  
     113    return pselect (nfds, rfds, wfds, xfds, timeout, sigmask);
     114  }
     115  
     116  #endif